Indicator for radio controlled airplanes



I June 11, 1946. icK 2,401,873.

INDICATOR FOR RADIO CO NTR OLLED AIRPLANES ,Filed Nov. 22, 1940 IN/ULAT/ON a: 1 INVENTOR Patented June 11, 1946 INDICATOR FOR RADIO CONTROLLED I AIRPLANES James B. Kendrick, Glendale, Calif., assignor, by mesne assignments, to Lockheed Aircraft Corporation, a corporation of California Application November 22, 1940, Serial No. 366,628

3 Claims. (01. 244 1) l 2 This invention relates to the provision of a Figure II i an enlarged detail of the velocity visual indication of the attainment of a desired responsive control. 1 critical altitude and airspeed on the part of a Figure III is an enlarged detail of the altitude remotely controlled robot airplane. control. v

- Such robot airplanes have been proposed fo Figure; IV is a detailed view, conventional use a targets, torpedo carriers, or for dangerform, of the series circuit connection, through ous photographic missions wherein it is not decontrols A and V- of Figure I when the airplane sired to risk the life of a pilot therein; and of is grounded. necessity must be controlled from great dis- As shown: tances, approaching the limit of visibility even The smoke trail system disclosed in the drawwith the aid of powerful aids to vision. At such ing is intended for use in an internal combusdistances it is extremely diflicultfito estimate the tion engine driven plane, wherein an exhaust altitude and air speed of the robot plane, and pipe I0 leading from engine cylinders H is utiit is an object of this invention to provide visual lized to vaporize and eject a suitable liquid, indications, automatically produced by the rowhich liquid will preferably be chosen for it's bot plane, to respond to adequate air speed and smoke producing and lasting properties, such as as a limitation of the desired altitude of flight. is used in skywriting, for example. I have found thus providing the operator with a visual signal that a mixture of ten part flushing oil and one 01' the normal or desired functioning of the robot part carbon tetrachloride produces satisfactory plane in response to radio signals'delivered by results, but I do not desire to limit myself to the operator. such a mixture. The liquid system comprises a It is a further object of this invention to protank I2 with a pipe l3 feeding the liquid to an vide an automatic visual signal system of the injection orifice II in the engine exhaust pipe type described that will release a smoke trail dur- [0, a pump I5 driven by. an electric motorl6 ing'normal and desired flight condition but will serving to control-the supply of liquid. A comcut oil the smoke as the airplane slows down to bination pump and motor such as the autopulse stalling speed, or rises above a predetermined is especially convenient, but other forms o pumps altitude, as a warning to the operator. which will both feed and control the flow of liquid,

It is also an object of thi invention to provide can be used with an elevated tank. It is not an automatically responsive signal system opernecessary to have the tank elevated as shown,

ated by the motion and altitude of a robot plane although if so arranged the pump should obstruct independently of the remote control thereof, the flow of liquid when not in operation.

whereby to provide a signal system unaffected by he p p l is a ged to be driven by, the control impulses transmitted to the airplane. usual electrical system of the airplane. in this It is another object of this invention to make case shown as a battery 1 terminal.

the airplane and its flight path visible at great which is ded at t A i e I 9 l ads m di tanc a an ai t t ground pilot; or operthe battery to ,a switch 20 controlled by the air on speed or velocity of flight, thence to an altitude 1g 15 th object of t invention to controlled. switch 2|, and thence to the motor l6.

vide a simple and self-contained automatic eonj' spetd 0r lo ity responsive control 20, trol of a smoke discharging apparatus that can .wmch t been i V Figure I f be applied to variom purposes without identificat on, comprises a sensitive bellows'22 in mg the attention or presence of an operator an air tight case 23, the interior of the bellows a being connected at to the velocity assa es 25 Other and further important obJects of this p g invention will be apparentfrom the disclosures in of Pltot tube whue the ex i r of the bellows is connected to the static passage 21 of the the specification and the accompanyi g drawlng- Pitot tube by a connection 28 to the airtight case.

This invention in its preferred form is illuswith this arrangement the bellows expands in trated in the drawing and hereinafter more fully proportion to the air speed or velocity to which describedthe Pitot tube is exposed. A bracket 29 supports A Preferred form f s invention is shown an insulated block 30 having a contact 3| adjadiagrammatically in the drawing, wherein: cent which a beam 32 is pivoted, the beam having Figure I is a diagrammatic showing of a smoke an electrical connection 33 through its pivot producing mechanism and an altitude and velocpoint 3! and being arranged with an adjusting ity coptrol therefor. screw 35 positioned to be contacted by an element terminal connection 36, so that connections 33' and 36 are closed by the downward movement of the beam 32, these connections being part of the circuit iii.

The altitude responsive control 21 requires no -case or pressure connections, but is otherwise identical with that previously described, except i v present preferred embodiment thereof, I desire that the fixed contact 3| is normally maintained closed by a constant upward bias on the'spring s' to close the circuit through the connection 3'! if the smoke trail is to be produced below a given altitude at which this contact is opened by the expansion of the gas orair within the bellows 22.

By selecting'a bellows having a motion of approximately eight thousandths of an inch for a" hundred foot change in altitude, with a. corresponding movement of twenty thousandths for afive mile'per hour change in speed, I'have found that an allowable beam movement of sixteen thousandths for the altitude control and forty thousandths for the air speed control will give satisfactory sensitivity of the order mentioned. By a suitable adjustment of thescrews 3535- it is possible to adjust the closing or opening movements of the contacts for a predetermined air speed and altitude.

In the operation of my invention, assuming it is desired to provide a smoke trail at all air speeds above a selected value and at all altitudes below the selected altitude, the set up will be as first described, namely using the contact 31 of the airspeed control and the contact 3| of the alti-' tude control. With the altitude bellows sealed at sea level, its expansion will be in'proportion to-altitude, and the air speed control will expandin proportion to the net velocity head on the Pitot tube, so that both bellows will close their circuits, which are in series in the electrical connection l9 between the battery and motor, under the desired operating conditions, operating the.

motor pump combination to inject fluid into the exhaust pipe [0. For better vaporization of the smoke producing fluid, it is desirable to lag or cover the exhaust pipe with asbestos or the like.

The contact 3| will remain closed until the craft rises'above a desired cruising altitude. If we assume after take-01f a climbing speed of 80 M. P. H., in case the speed reaches 120 M. P.

(the desired cruising speed) during its climb, the

contact 3| will 'beclosed and a smoke indication is produced. The operator will then nose up the craft to'drop the speed below 120 M. P. H. to prevent smoke from forming. A desired operation depends mainly upon the feel of the operator matter for the operator to produce intermittent smoke signals during ascent by increasing and decreasing the speed. When the desired altitude is reached and exceeded, the altitude contact 3| willop'en with the result that no smoke signal will be produced. The operator by his knowledge indication more or less continuous at a normal cruising speed and altitude.

It will be evident that instead of using both altitude and air speed controls in series they can I be used to discharge separate smoke trails, which i might be of different color for identification pursmoke signal device to provide a. visual' indica tion of the flight path of a remotely controlled mechanism, such as a robot airplane, at a predetermined altitude and airspeed. Such a signal device mightalso be used for remotely controlled torpedo boats, to indicate speed and/or other "critical functions thereof.

Having thus described my invention and the i to emphasize the fact that many modifications may be resorted to in a manner limited onlyby a just interpretation of the following claims.

I claim as my invention: 1. In a device of the class described for use'on a robot airplane, means for injecting a smoke opening one of said pairs of contacts when: the airplane reaches predetermined altitude, and an airspeed IeSPollSlVGxbBlloWs having'mean's for closing .theother pair of contacts when the. airselected altitude. I 2. In a device of the class described-for use on.-

, and his 'skill with the controls. It will be a simple plane speed rises above a normal cruising speed whereby the. fluid will be injected intouthe exhaust pipe at speeds abovezanormal cruising. a predetermined" speed and at an altitude below a robot .airplane,.means for injecting a smoke producing fluid into theeXhaust-pipe of an in -i ternal combustion engine, means for. energizing.

and controlling said injection means-comprising anelectrical circuit having pairs .of switches arranged in series in. said circuit, said switcheseach comprising apivotedbeam movable to closeand open saidcircuit, an altitude responsive bellows having means for moving a respective beamtoopen one of said switches when the airplane reaches a. predetermined altitude, and an airspeed responsive bellows having means for mov-. ing the other beam to close the other of. said switches at'a predetermined air speed on-the" airplane'above a normal cruising speed whereby the fluid will be injectedinto therexhaustpipe.

at speeds above a normal cruising speed and at an altitude/below a predetermined selected althtudc.

3. In a robot airplane, means thereon for pros ducing a smoke stream signal to indicatefrom the ground more clearly the position'of the airplane, said means comprising an electrical circuit for energizing and controlling the signal producing meanspairs of circuit-closing contacts ar-v ranged inseries in said circuit, an altitudere sponsive'bcllows having meansfor opening one.

of said pairs of contacts when the airplane reaches apredeterminedaltitude, and an airspeed responsive bellows having means for C- .ing the other pair of contacts when the airplane speed rises above a normal cruising speed whereby the smoke signal will be produced at speeds above a normal cruising speed and at an altitude below a predetermined selected altitudep JAMES B. KENDRICK. 

